A few ebuilds uses flags, that are not set for them:
'media-sound/phonon-4.3.50_pre20090520:0::gentoo' has no flag named 'aqua'
'media-sound/phonon-4.3.1:0::gentoo' has no flag named 'aqua'
'kde-base/kcron-4.3.95:4.4::kde' has no flag named 'prefix'
There is 4.3.80 that satisfy the useflag aqua.
Prefix is portage internal useflag not added to iuse.
So we dont bother with flaws of not entirely supported package manager.
dunno who should handle this.